1. Summary of the Invention
This invention relates to an improved tamper switch assembly, wherein the mechanical wiping contacts of known tamper switch designs are removed, and replaced by a magnetically actuatable switch assembly, and associated bar magnet. In the preferred embodiment, a standardized tamper switch housing is employed so that the present invention can have widest applicability for replacement of mechanical wiper type tamper switches assembly, without necessitating any modification to mounting arrangements now fairly standarized in the industry, for tamper switches.
As a matter of background, tamper switches are very commonly used with respect to alarm systems, and a given alarm externally mounted bell box, for example, will have a first tamper switch to indicate whether an access door is being opened, and a second tamper switch to indicate whether the entire box is being removed from its mounting surface. Because such bell boxes are exposed to marine atmospheres, and severe weather environments generally, prior experience with known and available forms of tamper switches has been very disappointing. The present invention predicates significant improvement upon the state of the prior art in tamper switches, through an invention which is characterized by maintaining, completely, the external geometry of conventional tamper switches, while only changing the interior functioning of the device to not only eliminate mechanical wiping of parts, but also to produce an unexpected function which was unexpected and particularly advantageous in its intended applications.
2. Brief Description of the Prior Art
Prior workers have designed magnetic reed switches in various formats, to solve particular problems. To the best knowledge of applicant there has been no realization that a certain juxtapositioning of magnet and switch elements, inside of a conventional tamper switch geometry, would produce the results which are taught herein.
Current known prior art devices are shown in the U.S. Pat. Nos., as follows:
Ellwood: 2,289,830 PA0 Posey: 3,579,159 PA0 Risk: 3,622,926 PA0 Takahashi: 3,710,369 PA0 Pedersen 3,736,397 PA0 Murphy: 3,792,389 PA0 Glay: 3,828,910 PA0 Maeda: 3,829,803 PA0 Peterson: 3,896,404 PA0 Porat: 3,932,718 PA0 Soulas et al.: 3,937,913 PA0 Peterson: 4,012,611 PA0 Solomon: 4,012,731 PA0 Chusha: 4,041,427 PA0 Haag et al.: 4,072,917 PA0 Sims, Jr.: 4,117,430 PA0 Hetzer: 4,130,745 PA0 Kondo et al.: 4,186,362
Various of the switch concepts illustrated in these patents eliminate a need for a wiping contact arrangement in a switch, by substitution of a non-contact arrangement, wherein a permanent magnet is moved proximate a sealed glass reed switch element. The Ellwood patent illustrates an early teaching on the concept of a reed switch, and is noted to illustrate the type of switch element which the present invention uses in a unique manner.
The Posey patent is particularly helpful to understanding of one unexpected feature of the present invention, in that his FIGS. 7 and 8 illustrate certain known interactions between reed switch contacts, which have high magnetic permeability and low magnetic retentivity, and a magnetic flux. It is the particular concern of the teachings in Posey to place a magnet so there will be a null position, wherein the switch will remain open, this occurs when the same polarity field enters both reed switch elements due to the symmetrical placement of his particular ceramic magnet proximate the overlap of the two reed elements. In direct contrast to the teachings of Posey, the present invention arranges the geometry of the device so that the movement of its plunger will be from a position where the contact reeds of the switch element are substantially unaffected by the magnetic fluxes of an elongated bar magnet, to a position where the one pole of the magnet is moved into proximity with only one of the blades inside of the encapsulated reed switch, to thereby oppositely polarize the two blades of the switch, and generate an attractive force between the blades which closes a circuit. The present invention focuses upon creating different longitudinal stations, depending on direction of movement, before a state of actuation changes.
The Takahashi patent illustrates a combination wherein a reed assembly is incorporated into a framework device, and is noted simply to illustrate one known alarm system application for reed switches.
The Pedersen patent illustrates a keyboard switch assembly application, wherein the improvement involves preventing formation of a partial vacuum when a key is pressed against a resilient surface, and also illustrates a bar magnet being moved in a parallel manner to a reed switch, by an actuating member.
The Glay patent illustrates different improvements in a keyboard design, such as that previously taught by Pedersen, and is also not particularly concerned with the problem which is addressed and solved by the present application. The present teachings are for a particularly long actuation stroke and geometry so the switch tends to remain closed to a point on its return stroke, that is above the point of closure of its actuating stroke.
The patent to Murphy, as well as the patent to Risk, illustrate a particular improvement wherein a reed switch is mounted longitudinally, and parallel with respect to the motion of a particular magnet. In contrast, the present invention is predicated upon the transverse mounting of a reed switch, wherein further the bar magnet, (which is both longitudinally disposed and also polarized in directions parallel to its axis) will be moved proximate only one end of the switch.
Takahashi and Peterson '404 both illustrates forms of architectural devices, wherein a magnetic switch is incorporated into either a framework, or a hinge, for example, and are examples of known, unique geometrical relationships using reed switch technology. The Maeda patent illustrates a seat detecting device, wherein particular pressure requirements in detecting presence of a person on a seat dictate that a bar magnet should be parallel to the reeds of a reed switch, with the spatial relationships between the reed and the magnet also contrary to the problem which is addressed and solved by the present invention. Similarly, Peterson '611 illustrates one specific pendulum-type juxtapositioning magnet and reed switch, to determine inertia changes, and further illustrates unexpected results are obtained by unique orientations of magnets and reed switches.
The Haag et al. patent illustrates another hinge including a reed switch assembly, wherein the cooperation of the elements appears hidden to the average observer.
The Solomon patent is noted to illustrate a self-contained burgular alarm system comprising a power source and certain motion sensing devices, and to show the category of devices for which the present invention teaches an improvement.
The patents to Chusha and Sims, Jr. illustrate fairly recently patented keyboard designs, wherein magnets are used to complete a circuit device. Chusha is helpful to understand the present invention insofar as it predicates improvement through disposing the n-s direction of a magnet oblique to the longitudinal direction of the reeds of a reed switch. The Chusha patent, as well as the previously-discussed patent to Posey, are helpful background to appreciate the magnetic fluxes generated by different polarity formats (see FIGS. 1 and 4 of Posey, for example), and one aspect of the present invention is to take advantage of the differential in a magnetic flux field.
The keyboard switch patent to Sims, Jr., as well as the intrusion detector patent to Porat, are further examples of unexpected results from particularly orienting a plunger and a magnet. Sims, Jr. teaches a plastic plunger that is magnetized in a circular manner, wherein the polymeric host material has iron particles suspended therewithin, and are ordered to produce a magnetic field which varies with the location of the actuator. The Porat patent illustrates a conventional bar magnet/reed switch arrangement wherein the magnet is moved parallel to the elongated direction of a reed switch, and illustrates prior efforts to develop a switching for only slight motions of the actuating device.
Finally, the Soulas et al. patent is noted to illustrate one inventor's approach to the problem of corrosion around a switch, through adaption of seals to a magnetically actuatable switch design.